From Tom's Hardware: We all know about "Windows rot," where the operating system slowly degenerates to a slow, sluggish state after numerous installs, uninstalls, and other things that a system accumulates over time.
Those of us who perform good housekeeping practices on our computers keep our Windows installs running better, longer, but that's not the case for everyone. The action of a fresh format and/or reinstall can make things feel new again, even on old hardware. And now it seems that Microsoft could be building a reinstall feature into Windows 8.
As seen in some of the leaked presentation slides, Microsoft could have a recovery option to "reset Windows" while retaining all personal files and user accounts. One of the presentation images shows the option of reinstalling all of the app purchases from the Microsoft App Store. Interesting stuff.
Interesting, IMO. To be honest with Windows XP and especially Windows Vista and later, I never found the need to reformat at any time with good housekeeping. But this is interesting nevertheless. Kind of like what Apple has been doing with the iPhone on the Restore feature? (It reloads the OS and files/apps, I have to use it since I jailbreak my phone)